Delayed optical router/switch

Abstract

A system, method, and apparatus for delayed optical router based on slow light and nondegenerate four-wave mixing processes are presented, in which three laser pulses interact with a three-level nonlinear optical medium composing two closely spaced ground states and an excited state. The delayed optical routing mechanism is based on a slow light phenomenon, in which a group velocity of an incoming input signal pulse is slowed down due to quantum coherence induced refractive index change. The two-photon coherence induced on the ground states via electromagnetically induced transparency is optically recovered via nondegenerate four-wave mixing processes. The nondegenerate four-wave mixing generation is enhanced owing to absorption cancellation. In this case, the individual pulse switching / routing time is limited by the coherence decay time that is much faster than population decay time, where the population decay-time is a limiting factor of conventional switching devices. In the present invention of the delayed optical router the overall switching / routing time, however, is controlled to be delayed by using the slow light. Even though the overall switching / routing time can be delayed, the switching bandwidth of the present invention is not degraded at all because the input and output signal's group velocity across the delayed optical router is still same. Therefore, the present invention of the delayed optical router gives an advantage of wide-bandwidth optical data traffic control using a narrow-bandwidth processing unit such as an electronic device. Another advantage is signal amplifications owing to the dark-resonance enhanced nondegenerate four-wave mixing processes.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method and apparatus for an optical switch and routing based on quantum coherence, specifically using slow light phenomenon and nondegenerate four-wave mixing processes.[0003]2. Description of the Related Art[0004]An optical router is a switching device applied to convert an optical signal into another one at different propagation direction with either the same frequency basis or not. The optical router is a subcategory of an optical switch that is in general used to drop, add, multiplex, or convert an optical signal into another one. In fiber-optic communications, as more data traffic increases, more information bandwidth is needed. In this case a wider bandwidth optical switch is obviously demanded. However preparation of wide bandwidth optical switch is not simply easy because of technical limitations in switching devices such as an inherently limited optical switching time and slow...

AI Technical Summary

Benefits of technology

[0010]The delayed optical router relaxes the switching performance because slow electronics whose speed is less than 4 GHz can control even faster optical-data traffic (˜40 Gbps) without degrading the overall traffic rate. For better understanding of this, let's carefully study the interface between air or a fiber and the nonlinear optical medium used for the present delayed optical router. At the front interface of it, the data traffic incident to the delayed optical router becomes slow down due to the slow group velocity. In more detail, the front part of the optical pulse envelope incident to the delayed optical router starts to compress in both space and time until the back part of the pulse envelope enters the medium. And then the compressed optical pulse propagates through the medium in a slow speed until it reaches at the back end of the medium. Here it should be noted that consecutive optical pulses entering the nonlinear medium (delayed optical router) do not collide each other at the interface even the propagation speed is very different. When the optical pulse leaves the medium at the back end, the front part of the optical pulse envelope starts to fly forward in a very high speed until the back part of the pulse envelope leaves the medium. Therefore the data traffic rate across the delayed optical router is invariant, and it is good advantage to the electronic counterparts to switch / route faster optical pulses.

Problems solved by technology

At the front interface of it, the data traffic incident to the delayed optical router becomes slow down due to the slow group velocity.

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